ARTHROPODA. 



99 



an oval thin-walled bladder (&/), which opens (st) externally on 

 the basal joint of the antenna. The green part is made up of a 

 single much-coiled tubule, lined by glandular epithelium. 



The kidney is richly supplied with blood, from which it separ- 

 ates nitrogenous waste in the form of guanin (C 5 H 5 N 5 O), and 

 uric acid (C 5 H 4 N 4 3 ), by means of its glandular epithelium. 



8. Reproductive Organs (Fig. 29). The sexes are distinct, 

 and the external differences between them chiefly consist in the 

 greater breadth of the abdomen in the female, and the modification 

 of the two first pairs of abdominal appendages in the male. 



(1) In the male crayfish (A) a single yellowish- white spermary 

 (testis) underlies the pericardial sinus. It possesses two short 



Fig. 29. REPRODUCTIVE ORGANS OF CRAYFISH. A, Male organs ; 



anterior and posterior lobes of spermary (testis); v.d, spermiduct (vas 

 deferens) ; g. o, style inserted into genital aperture. B, Female organs ; 

 ov and ov', anterior and posterior lobes of ovary; od, oviduct; y.o, 

 genital opening. The ovary has been cut open on one side to expose 

 its cavity. 



anterior lobes (t), which broaden behind, and a longer and narrower 

 posterior lobe (t'). A slender spermiduct (vas deferens) (v.d) arises 

 on each side from the junction of the lobes, enlarges considerably, 

 and, after many convolutions, runs downwards to one of the male 

 genital pores (g.o), situated on the proximal joint of the last pair 

 of walking-legs. 



The spermiducts branch repeatedly within the spermary, their 

 finest branches ending in minute lobules, each of which is formed 

 by a small group of vesicles lined by mother-sperm-cells. Each 

 of these divides, before the breeding-season, and gives rise to a 

 number of spermatocytes, which develop into minute nucleated 

 sperms, rounded and somewhat flattened, with a number of delicate. 



